This invention relates to the way of replacement of main seals in a ball valve and a ball valve.
There are known ball valves with possibility of repairing them in an emergency situations without the necessity of disassembly of valves from a gas piping.
Nowadays, there are widely offered valves with the possibility of replacement of stem seals without the necessity of cutting off or detachment of such a valve from a gas piping but ball valves of a type “Top Entry.” e.g., which a construction that enables removing a ball closing component from a body and replacing main seals, e.g. seals of the body, with the ball closing component without disassembly of the valve from a gas piping are still used very rarely.
Previously mentioned valves have a body inside of which there is a ball closing component, seal assemblies located slidably in the recess of the body, and of a stem with seals. The body is closed by a cover. Each of the seal assemblies contains a seating ring, called also a mounting, having a seal placed from a side of the ball closing component.
There is a shaped spring, made of an elastic wire, among the seating ring and seal rings placed in the rear part of a recess which ensures leak tightness at small pressures. Free ends of the spring are bent.
After cutting off a gas supply, degassing of the valve, dismounting of the stem and removing a cover these springs are put forward, which enables shifting of mountings of main seals along a passage axis of the main valve and taking the ball closing component out of the body and then dismounting seating rings in order to replace or repair scales. In the above mentioned case leak tightness at high pressures is ensured first of all by pressure of gas on floating mountings of main seals, as there is a lack of full spring compensation.
The above solution is proportionally simple, but as a result of using two gradual seals there may be problems with leak tightness at indirect pressures, e.g., pressures which are between little and mean pressures and between mean and high pressures.
Moreover a shape of the spring does not ensure equal pressure on the whole circuit.